Two sources told Reuters that Nissan is looking to sell its 51 percent stake in Automotive Energy Supply Corporation, a company that builds lithium-ion batteries for automotive use. NEC Corporation has joint ownership.

Also, Japanese newspaper The Nikkei reported that Nissan was looking to sell because it would be cheaper for them to buy batteries for electric cars it builds, including the Nissan Leaf, from other automakers. The Nikkei did not source its claims.

With the expectation that the EV market will grow comes increased competition to build batteries to supply the juice for electric vehicles.

“The latest reporting on Nissan and its battery business is speculation, and is not based on any announcement by us,” a Nissan spokesperson told us. “Nissan is committed to producing the best possible EV solutions for our customers. To that end, we continuously evaluate our business strategy in pursuit of optimal products and business structure.”

Rival Tesla has a goal of building 500,000 vehicles – all EV – by 2018. Tesla gets its batteries from Panasonic, although it’s also building a gigafactory to increase production.

Nissan and corporate partner Renault said in 2009 that they’d invest $4.43 billion to build the Leaf, other EVs, and up to 500,000 batteries to help power those vehicles.

Lower than expected sales have made it hard for Nissan and NEC to lower costs through mass production, however.

Reuters reported two years ago that Nissan was planning to cut production at Automotive Energy Supply Corporation in favor of using batteries from LG Chem.

Nissan may also be in talks to sell a 41-percent stake in auto-parts supplier Calsonic Kensei Corp. Meanwhile, Nissan agreed to purchase a 34-percent stake in Mitsubishi Motors for around $2.2 billion, as a way to better compete with larger rivals such as Toyota and Volkswagen.